[lammps-users] reax cross-language link

These are Makefile errors, not LAMMPS errors per se.
You don't have some of the libs you are trying to
link against. So whatever Fortran compiler you used
for ReaxFF, it must provide other libs. You need to
find out what those are and specify them in your Makefile.

I suggest you find a local person who is familiar with
building codes, cross-language links, and Makefiles.